Halogenated benzoxazine for use in the synthesis of polybenzoxazine

ABSTRACT

A halogenated benzoxazine compound, which can be used in particular as monomer in the synthesis of polybenzoxazine, corresponds to the formula: 
                         
in which: each benzene nucleus of the two oxazine rings bears at least one halogen (represented by the symbol Hal), in particular bromine, chlorine or fluorine; and Z 1  and Z 2 , which are identical or different, represent an aliphatic, at least divalent, bonding group comprising at least one carbon atom and optionally at least one heteroatom chosen from O, S, N and P.

1. FIELD OF THE INVENTION

The present invention relates to monomers which can be used in thesynthesis of thermosetting resins, intended in particular for adhesivesystems which make possible in particular the adhesive bonding of metalto rubber.

It more particularly relates to benzoxazine compounds suitable for thesynthesis of polybenzoxazines which can be used in particular asadhesive layers in metal/rubber composites intended for the manufactureof rubber articles, such as pneumatic or non-pneumatic tyres, forvehicles.

2. STATE OF THE ART

Metal/rubber composites, in particular for vehicle tyres, are wellknown. They are most often composed of a matrix made of rubber,generally diene rubber, which can be crosslinked with sulfur, comprisingmetal reinforcing elements (or “reinforcers”), such as threads, films orcords made of carbon steel.

As they are subjected to very high stresses during the rolling of thetyres, in particular to repeated actions of compression, bending orvariation in curvature, these composites must, in a known way, satisfy alarge number of sometimes contradictory technical criteria, such asuniformity, flexibility, flexural strength and compressive strength,tensile strength, wear resistance and corrosion resistance, and mustmaintain these performance qualities at a very high level for as long aspossible.

It is easily understood that the adhesive interphase between rubber andreinforcers plays a dominating role in the endurance of theseperformance qualities. The conventional process for connecting therubber compositions to carbon steel consists in coating the surface ofthe steel with brass (copper/zinc alloy), the bonding between the steeland the rubber matrix being provided by sulfurization of the brassduring the vulcanization or curing of the rubber. In order to improvethe adhesion, use is generally made, in addition, in these rubbercompositions, of organic salts or metal complexes, such as cobalt salts,as adhesion-promoting additives.

In point of fact, it is known that the adhesion between the carbon steeland the rubber matrix is liable to weaken over time as a result of thegradual development of the sulfides formed, under the effect of thevarious stresses encountered, in particular mechanical and/or thermalstresses, it being possible for the above degradation process to beaccelerated in the presence of moisture. Moreover, the use of cobaltsalts renders the rubber compositions more sensitive to oxidation and toageing, and significantly increases the cost thereof, not to mentionthat it is desirable to eliminate, in the long run, the use of suchcobalt salts in rubber compositions due to recent developments inEuropean regulations relating to metal salts of this type.

For all the reasons set out above, manufacturers of metal/rubbercomposites, in particular vehicle tyre manufacturers, are seeking noveladhesive solutions in order to adhesively bond the metal reinforcers tothe rubber compositions, while overcoming, at least in part, theabovementioned disadvantages.

Thus it is that the recently published applications WO 2014/063963, WO2014/063968, WO 2014/173838 and WO 2014/173839, filed by the ApplicantCompanies, have described novel polymers comprising urea, urethane orthiourea units, and also their starting monomers, which meet the aboveobjectives. Used in particular as adhesion primer on metal inmetal/rubber composites, these polymers make it possible veryadvantageously to adhesively bond the metal to the rubber matrices bysubsequently using simple textile adhesives, such as “RFL”(resorcinol/formaldehyde latex) adhesives or other equivalent adhesivecompositions, or else directly (that is to say, without employing suchadhesives) to these rubber matrices when the latter contain, forexample, appropriate functionalized unsaturated elastomers, such asepoxidized elastomers. Thus, the cobalt salts (or other metal salts) canin particular be dispensed with in the rubber compositions intended tobe connected to brass-coated metal reinforcers.

On continuing their research studies, the Applicant Companies have founda novel benzoxazine compound, which can be used as monomer in thesynthesis of a polybenzoxazine, of the thermosetting type, which, atambient temperature, exhibits the same adhesive performance qualities,with regard to the metal and the rubber, as the abovementioned polymersbut which exhibits, once thermoset (crosslinked), a thermal and chemicalstability which is again improved and the specific microstructure ofwhich additionally makes it possible very advantageously to adjust theflexibility of the molecule according to the particular applicationstargeted.

3. SUMMARY OF THE INVENTION

The present invention relates to a halogenated benzoxazine correspondingto the formula (the symbol “Hal” representing a halogen):

in which:

-   -   each benzene nucleus of the two oxazine rings bears at least one        halogen;    -   Z₁ and Z₂, which are identical or different, represent an        aliphatic, at least divalent, bonding group comprising at least        one carbon atom and optionally at least one heteroatom chosen        from O, S, N and P.

By virtue of this specific benzoxazine, it is possible to preparebenzoxazine polymers or “polybenzoxazines” which have the remarkableability, at high temperature, to open their oxazine rings and to thusresult in a thermosetting polyphenol resin structure. This confers onthem, in comparison with the other known polymers described in theintroduction to the present document, a better thermal stability.Finally, its specific microstructure makes it possible veryadvantageously to adjust the flexibility of the polybenzoxazinesdepending on the particular applications targeted.

The invention also relates to the use of a compound in accordance withthe invention in the synthesis of a polybenzoxazine, and also to anypolybenzoxazine resulting from at least one benzoxazine compoundaccording to the invention.

The invention also relates to any process for the synthesis of apolybenzoxazine by polycondensation of a compound according to theinvention, in particular with, as second monomer, an aromatic diol orthiol compound.

4. BRIEF DESCRIPTION OF THE FIGURES

The invention and its advantages will be easily understood in the lightof the detailed description and of the implementational examples whichfollow, and also of FIGS. 1 to 11 relating to these examples, whichrepresent or diagrammatically represent:

-   -   the general principle for the synthesis of a benzoxazine        compound starting from three compounds, phenol, formaldehyde and        amine (R=residue of the amine) (FIG. 1a );    -   the mechanism for opening, by heat input, the oxazine ring        (ring-opening) of such a benzoxazine compound (FIG. 1b );    -   a general scheme for the synthesis, starting from a halogenated        phenol (Hal representing a halogen), paraformaldehyde and a        specific aromatic diamine, of a halogenated benzoxazine in        accordance with the invention of formula (A), which can be used        as monomer (Monomer denoted “M”) in the synthesis of a        polybenzoxazine (FIG. 2);    -   a possible scheme for the synthesis, starting from a halogenated        phenol, paraformaldehyde and a specific diamine of the aromatic        type, of a particular halogenated benzoxazine according to the        invention of formula (A-1), which can be used as monomer        (Monomer denoted M-1) in the synthesis of a particular        polybenzoxazine (FIG. 3);    -   a general scheme for the synthesis of a polybenzoxazine polymer        (Polymer denoted “P”) starting from the halogenated benzoxazine        of the invention of formula (A) (Monomer M) of FIG. 2 and        another monomer of generic formula (B) (Monomer denoted “N”) of        aromatic diol or thiol type (FIG. 4);    -   a scheme for the synthesis of a particular polybenzoxazine        polymer (Polymer denoted P-1), starting from a particular        halogenated benzoxazine according to the invention of formula        (A-2) (Monomer M-2) and another particular monomer of formula        (B-1) (Monomer N-1) of the sulfur-comprising aromatic diol type        (bearing a thioether functional group) (FIG. 5);    -   a scheme for the synthesis of another polybenzoxazine (Polymer        denoted P-2), starting from the particular halogenated        benzoxazine according to the invention of formula (A-2) (Monomer        M-2) of the preceding FIG. 5 and another particular monomer of        formula (B-2) (Monomer N-2) of the aromatic thiol type (bearing        an ether functional group) (FIG. 6);    -   a scheme for the synthesis of another polybenzoxazine (Polymer        denoted P-3), starting from the halogenated benzoxazine        according to the invention of formula (A-2) (Monomer M-2) and        another particular monomer of formula (B-3) (Monomer N-3) of the        aromatic thiol type (bearing a thioether functional group) (FIG.        7);    -   the polybenzoxazine (Polymer denoted P′ here) of FIG. 4 once its        oxazine rings have been opened after heat treatment of the        Polymer P (FIG. 8);    -   the particular polybenzoxazine (Polymer denoted P-1′) of FIG. 5,        once its oxazine rings have been opened after heat treatment of        the Polymer P-1 (FIG. 9);    -   the scheme for the synthesis, starting from a brominated phenol        (compound 1), paraformaldehyde (compound 3) and a specific        aromatic diamine (compound 2), of a particular brominated        dibenzoxazine according to the invention of formula (A-3)        (Monomer denoted M-3) which can be used in the synthesis of        polybenzoxazines (Polymer P-4 and P-4′ of FIG. 11) (FIG. 10);    -   the scheme for the synthesis of a particular polybenzoxazine        (Polymer denoted P-4), starting from the particular halogenated        benzoxazine according to the invention of formula (A-3) (Monomer        M-3) of the preceding FIG. 10 and the particular monomer of        formula (B-1) (Monomer N-1), and also the structure of this        polymer once its oxazine rings have been opened (Polymer denoted        P-4′) (FIG. 11).

5. DETAILED DESCRIPTION OF THE INVENTION

It will first of all be recalled that benzoxazines are compounds ofgeneral formula:

The appended FIG. 1a recalls the general principle of the synthesis of abenzoxazine, in this instance starting (condensation reaction) from onemolecule of phenol, from two molecules of formaldehyde and from an amine(R denoting the residue of the amine), with elimination of two moleculesof water.

FIG. 1b for its part recalls the mechanism for opening the oxazine ring(ring-opening) of such a compound during a heat input (represented bythe symbol A).

Numerous benzoxazine compounds or monomers can thus be synthesized usingvarious phenols and amines depending on their types of substituents.These substituting groups may subsequently provide polymerizable sitesand make possible the synthesis of various benzoxazine polymers (orpolybenzoxazines).

Benzoxazines and polybenzoxazines which result therefrom are productswhich are today well known to a person skilled in the art; to cite but afew publication examples, mention may be made of the papers“Polybenzoxazines—New high performance thermosetting resins: synthesisand properties”; N. N. Ghosh et al., Prog. Polym. Sci., 32 (2007),1344-1391, or “Recent Advancement on Polybenzoxazine—A Newly DevelopedHigh Performance Thermoset”, Y. Yaggi et al., J. Polym. Sci. Part A:Polym. Chem., Vol. 47 (2009), 5565-5576, and also, for example, of thepatents or patent applications U.S. Pat. No. 5,543,516 and WO2013/148408.

As explained in detail in the above documents, polybenzoxazines have theremarkable ability, at high temperature (for example, typically greaterthan 150° C., indeed even greater than 200° C., depending on theirparticular microstructure), to open their oxazine rings and to thusresult in thermosetting polyphenol resin structures.

The specific benzoxazine of the invention, designated “Monomer M” in thepresent patent application, is of the halogenated type; it correspondsto the generic formula (A) which follows, Hal representing a (at leastone, that is to say one or more) halogen:

The appended FIG. 2 gives the general scheme for the synthesis thereof,under heat input and with elimination of water, starting from ahalogenated phenol, paraformaldehyde and a diamine.

In the formula (A) above, Z₁ and Z₂, which are identical or different,represent a bonding (spacer) group which is at least divalent, that isto say that they might comprise more than two covalent bonds, forexample three or four covalent bonds. Preferably, Z₁ and Z₂ aredivalent, that is to say comprise only two covalent bonds.

Z₁ and Z₂ are aliphatic. These groups, which can be ethylenicallysaturated or unsaturated, comprise, by definition, at least one (that isto say, one or more) carbon atom, and optionally at least one (that isto say, one or more) heteroatom chosen from O (oxygen), S (sulfur), N(nitrogen) and P (phosphorus).

According to a particular embodiment of the invention, Z₁ and Z₂, whichare identical or different, represent an aliphatic group comprising from1 to 12, more preferably from 1 to 8, in particular from 1 to 6, carbonatoms. More preferably still, Z₁ and Z₂, which are identical ordifferent, represent a (poly)alkylene (or alkylidene) sequencecomprising from 1 to 8, preferably from 1 to 6, in particular from 1 to4, carbon atoms.

More particularly, the compound of the invention corresponds to theformula:

in which x₁ and x₂, which are identical or different, represent aninteger from 1 to 8, preferably from 1 to 6, in particular from 1 to 4.

Each benzene nucleus of the two oxazine rings of the Monomer M bears atleast one (that is to say, one or more) halogen, this halogen preferablybeing bromine (Br), chlorine (C1) or fluorine (F), more preferablybromine.

Moreover, in this monomer of formula (A), one or more hydrogen atoms ofat least one or of each of these benzene nuclei can be substituted (ornot) by various substituents, for example by functional groups capableof promoting the adhesion of the polymer to the metal and/or to therubber. Likewise, at least one (that is to say, one or more) hydrogenatom of the phenylene group (or central benzene nucleus positionedbetween Z₁ and Z₂) might also be substituted by different substituents,for example by such functional groups also capable of promoting theadhesion of the polymer to the metal and/or to the rubber.

Preferably, each benzene nucleus of the two oxazine rings of thecompound according to the invention bears a single halogen (Hal) or atmost two, more preferably one and only one halogen, the latter beingmore preferably located in the para position with respect to the oxygenof the oxazine ring.

Thus, according to a particularly preferred embodiment, the compound ofthe invention corresponds to the formula:

in which x₁ and x₂, which are identical or different, represent aninteger from 1 to 8, preferably from 1 to 6.

According to a particularly preferred embodiment, Hal representsbromine.

FIG. 3 illustrates a possible scheme for the synthesis, starting from aspecific diamine of the aromatic type, of a particular halogenatedbenzoxazine according to the invention of formula (A-1), thisbenzoxazine being able to be used as monomer (Monomer denoted M-1) inthe subsequent synthesis of a polybenzoxazine. It is noted that, Z₁ andZ₂ represent —(CH2)x1- and —(CH2)x2- respectively vary, in whichformulae the symbols “x1” and “x2” represent an integer preferablyranging from 1 to 12, more preferably from 1 to 8, in particular from 1to 6. Such a synthesis will be described in greater detail in theimplementational examples which follow (FIG. 10).

The benzoxazine in accordance with the invention of formula (A)described above is intended in particular (as Monomer M) for thesynthesis of a polybenzoxazine by polycondensation, in particular bypolycondensation with at least one aromatic diol or thiol compound assecond monomer (“Monomer N”) having the formula (B):HX₁—Ar₁—Z₃—Ar₂—X₂Hin which:

-   -   X₁ and X₂, which are identical or different, represent O        (oxygen; case of a diol monomer) or S (sulfur; case of a thiol        monomer);    -   Ar₁ and Ar₂, which are identical or different, represent a        phenylene group;    -   Z₃ represents O or (S)_(n), the symbol “n” representing an        integer equal to 1 (case of a single sulfur atom) or greater        than 1 (case of several sulfur atoms).

In the generic formula (B) above, there is preferably at least one ofthe following characteristics which is confirmed:

-   -   X₁ and X₂ each represent either a sulfur atom or an oxygen atom;    -   Z₃ represents O or S (i.e. “n” equal to 1), more preferably S.

More preferably, it is all of the preferred characteristics above whichare confirmed simultaneously.

Moreover, in the formula (B) above, one or more hydrogen atoms of atleast one or of each Ar₁ and Ar₂ group can be substituted (or not) by asingle or several substituents, which are identical or different, forexample by functional groups capable of promoting the adhesion of thepolymer to the metal and/or to the rubber.

Mention may be made, as examples of Monomers N (diols or thiols)preferably suitable for the invention, of the Monomers respectivelydenoted N-1, N-2 and N-3 in FIGS. 5, 6 and 7, which figures arecommented on subsequently, which monomers are of respective formulae(B-1), (B-2) and (B-3) below:

Thus, the benzoxazine in accordance with the invention of formula (A) isintended in particular for the synthesis of a polybenzoxazine (Polymerdenoted “P”) comprising repeating structural entities comprising atleast one unit corresponding to the formula (I) (before opening of theoxazine rings) or formula (II) (after opening of the rings) below:

in which formulae (I) and (II) above Z₁, Z₂ and Z₃ have the maindefinition and the preferred definitions already given above.

Polymer should be understood here as meaning any homopolymer orcopolymer, in particular block copolymer, with repeating structuralentities comprising at least one unit of formula (I) or (II) above; thispolymer can, of course, comprise both units of formula (I) and units offormula (II).

In the formula (II) above, a person skilled in the art will immediatelyunderstand that the two symbols “*” (which are identical or different)represent any attachment of the unit to a carbon atom or to a heteroatom(preferably chosen from O, S, N and P), which attachment or bond resultsfrom the opening of the oxazine rings.

FIG. 4 represents a general scheme for the synthesis, bypolycondensation, of such a polybenzoxazine (Polymer P), starting fromthe halogenated benzoxazine according to the invention of formula (A) ofFIG. 2 (Monomer M) and from another monomer, of generic formula (B),which is of the aromatic diol or thiol type (Monomer N).

The polybenzoxazine of FIG. 4, more precisely at least a portion of itsrepeating entities, has also been represented in FIG. 8, before (PolymerP) and after (Polymer P′) opening of the oxazine rings.

FIG. 5 represents a particular scheme for the synthesis of a specificpolybenzoxazine (Polymer denoted P-1) of formula (I-1), starting from aparticular halogenated benzoxazine according to the invention (MonomerM-2) of formula (A-2) and from another specific monomer (Monomer N-1) offormula (B-1) of the sulfur-comprising aromatic diol type(4,4′-thiodiphenol).

In this example, it is noted in particular, according to a preferredembodiment of the invention already described, that each benzene nucleusof the benzoxazine (Monomer M-2) in accordance with the invention bearsone and only one halogen (Hal), more preferably bromine, this halogenbeing more particularly located in the para position with respect to theoxygen of the oxazine ring.

This polybenzoxazine of FIG. 5, or more precisely at least a portion ofits repeating entities, has also been represented in FIG. 9, before(Polymer P-1) and after (P-1′) opening of its oxazine rings following asufficient heat input.

Thus, according to a particularly preferred embodiment, thepolybenzoxazine resulting from the benzoxazine of the invention ischaracterized by repeating entities comprising at least one unitcorresponding to the particular formulae (I-1) (before opening of thebenzoxazine rings) or (II-1) (after opening of the rings):

FIG. 6 represents another scheme for the particular synthesis of anotherspecific polybenzoxazine (Polymer denoted P-2) of formula (I-2),starting from the preceding specific halogenated benzoxazine of theinvention (Monomer M-2) and from another specific monomer (Monomer N-2)of formula (B-2) of the aromatic thiol type (additionally bearing anether functional group).

FIG. 7 represents another scheme for the particular synthesis of anotherspecific polybenzoxazine (Polymer denoted P-3) of formula (I-3),starting from the preceding specific halogenated benzoxazine of theinvention (Monomer M-2) and from another specific monomer (Monomer N-3)of the aromatic thiol type (additionally bearing a thioether functionalgroup).

In these examples of FIGS. 6 and 7, as for the preceding FIG. 5, it isnoted in particular, according to a preferred embodiment of theinvention already indicated, that each benzene nucleus of the twooxazine rings of the benzoxazine of the invention bears one and only onehalogen (Hal), more preferably bromine, more particularly located in thepara position with respect to the oxygen of the oxazine ring.

As already indicated, FIGS. 8 and 9 also represent the polybenzoxazinesrespectively denoted P′ and P-1′ of FIG. 4 and FIG. 5, once theiroxazine rings are open.

Typically, the polybenzoxazine resulting from the benzoxazine compoundof the invention can comprise from ten to several hundred, preferablyfrom 50 to 300, structural entities having units of formula (I) and/or(II), in particular structural entities as represented by way ofexamples in FIGS. 5 to 9 and 11.

This polybenzoxazine resulting from the benzoxazine of the invention canadvantageously be used, as adhesion primer or as sole adhesive layer, inorder to coat a metal substrate, at the very least a substrate of whichat least the surface is at least partially metallic, and to cause thesubstrate to adhere to rubber. It can very particularly be used on anytype of metal reinforcer, such as, for example, a thread, a film or acord made of steel, in particular of carbon steel, intended inparticular to reinforce a matrix of unsaturated rubber, such as naturalrubber. Any known adhesive system, for example a conventional textileadhesive of the RFL (resorcinol/formaldehyde latex) type, can also beused to cause the rubber to adhere to the polybenzoxazine layer. Aperson skilled in the art will readily understand that the connectionbetween the metal substrate provided with its polybenzoxazine layer andthe rubber layer with which it is in contact will be definitivelyprovided during the final curing (crosslinking) of the rubber article inquestion.

6. EXAMPLES OF THE INVENTION

In the present patent application, unless expressly indicated otherwise,all the percentages (%) shown are % by weight.

The tests which follow describe first of all the synthesis of apreferred benzoxazine compound (Monomer M-3) in accordance with theinvention, of formula:

Then, the synthesis is described, starting from this monomer M-3, of apolybenzoxazine (Polymer P-4) of formula (I-4):

Finally, adhesion tests are carried out in order to illustrate theexcellent adhesive performance of the polybenzoxazines resulting fromthe benzoxazines of the invention.

5.1. Synthesis of a Halogenated Benzoxazine in Accordance with theInvention (Monomer M-3)

For this synthesis, a 250-ml three-necked round-bottomed flask, equippedwith a thermometer, a nitrogen inlet, a magnetic stirrer and acondenser, is provided.

The synthesis is carried out according to the procedure diagrammaticallyrepresented in FIG. 10, as explained in detail below, starting fromthree compounds: a halogenated phenol (compound 1; 4-bromophenol;Aldrich product B75808), an aromatic diamine (compound 2;p-xylylenediamine; TCI Europe product D1018) and paraformaldehyde(compound 3; Aldrich product 158127), in the presence of two solvents(anhydrous toluene and anhydrous ethanol).

Compound 1 (2 eq., 10.38 g, i.e. 60 mmol) and then ethanol (51 ml) arepoured into the round-bottomed flask. The presence of ethanol isimportant here, preventing the formation of an unstable intermediate ofthe triazine type. Compound 2 (1 eq., 4.13 g, i.e. 30 mmol), compound 3(4 eq., 3.60 g, i.e. 120 mmol) and finally the toluene (102 ml) aresubsequently introduced with stirring. The reaction medium is heated(approximately 75° C.) at reflux for 51 h and then the solvents andvolatile residues are distilled off at 110° C. (under vacuum of 1 mbar)for evaporation. The final product is subsequently washed (100 mlmethanol) and dried; a yellow-coloured powder is thus obtained.

This powder is placed in methanol (100 ml per 15 g of powder) and themixture is heated at reflux (65° C.) for 30 min. The solution is thenleft to cool to ambient temperature (approximately 20° C.) forcrystallization of the monomer. The solid product obtained is isolatedby filtration (Buchner filter). A white-coloured powder is thusobtained, after drying in an oven under vacuum at 50° C. overnight(reaction yield equal to approximately 82%).

The ¹H NMR spectrum (500 MHz) of the Monomer M-3 thus synthesized,dissolved in d8-THF, confirmed its chemical structure, with thefollowing results:

3.87 (s, 4H), 3.92 (s, 4H), 4.86 (s, 4H), 6.66-6.68 (d, 2H), 7.09-7.10(d, 2H), 7.19-7.22 (d, 2H), 7.31 (s, 4H).

5.2. Synthesis of a Polybenzoxazine (Polymer P-4)

This synthesis is carried out according to the procedurediagrammatically represented in FIG. 11, as described in detail below,starting from two monomers: the benzoxazine of the invention obtained inthe preceding stage (Monomer M-3) and the sulfur-comprising aromaticdiol of formula (B-1) (4,4′-thiodiphenol; Monomer N-1) already describedin FIG. 5; this being in the presence of sodium carbonate (Na₂CO₃; SigmaAldrich product 13418), and of (anhydrous) solvents DMA(N,N-dimethylacetamide; Sigma Aldrich product 38839) and toluene (AcrosOrganics product No. 364411000). The two monomers (M-3 and N-1) aredried beforehand under vacuum (10 mbar) at 60° C. overnight, andlikewise for the sodium carbonate but at a temperature of 150° C.

The synthesis is carried out in a 100-ml four-necked round-bottomedflask, equipped with a nitrogen inlet, a thermometer, a magnetic stirrerand a Dean-Stark separator surmounted by a condenser and by adistillation bridge (provided with a heating mantle). The apparatus isdried under vacuum using a hot air gun until the thermometer reaches atemperature of at least 100° C. in the reaction round-bottomed flask.Everything is left to cool to ambient temperature (20° C.) and then theapparatus is placed under a stream of nitrogen throughout the synthesis.

First of all, the Monomer M-3 (1 eq., 1.48 g, i.e. 2.79 mmol) of formula(A-3) and then the Monomer N-1 of formula (B-1) (1 eq., 0.61 g, i.e.2.79 mmol) are then introduced into the round-bottomed flask. Theaddition is subsequently carried out of 20 ml of DMA (solvent of bothmonomers) and then, as base, of Na₂CO₃ (3 eq., 0.89 g, i.e. 8.36 mol) insuspension in 4 ml of toluene. Everything is purged under N₂ for 5 minand then the reaction medium is heated to 105° C. Once this temperatureis reached (heating mantle temperature of approximately 115° C.), thedistillation bridge of the Dean-Stark apparatus is heated to 110° C.(with the heating mantle) in order to facilitate the azeotropicdistillation (water/toluene distillation) carried out for approximately90 min. The temperature of the reaction medium is then graduallyincreased, in stationary phases of 10° C. every 30 min, until 130° C. isreached. The reaction medium is left at this temperature for 17 h andthen it is left to cool to ambient temperature (20° C.). The reactionmedium is subsequently distilled at 90° C. (vacuum 3 mbar), in order toremove solvents and volatile residues, and then the solid precipitatethus obtained is washed with 250 ml of distilled water; during thiswashing, in order to extract the carbonate, acid (1% aqueous HCl) isadded dropwise until neutral pH is reached. The precipitate is onceagain washed with 100 ml of distilled water and dried under vacuum at80° C. overnight (approximately 12 h).

The Polymer P-4 of FIG. 11 was thus obtained, as attested to by the ¹HNMR analysis (500 MHz) in the solvent d8-THF, which gave the followingresults:

7.35 (br, 4H), 7.21 (br, 2H), 7.08-7.14 (br, 6H), 6.62-6.68 (br, 6H),4.87 (br, 4H), 3.1-4.4 (br, 8H). 3.1-4.4 (br, 8H).

This Polymer P-4, in the form of a red-coloured (rust-coloured) powder,was also analysed by DSC (Differential Scanning calorimetry) between−80° C. and +250° C. along a gradient of 10° C./min (Mettler Toledo“822-2” DSC device; nitrogen atmosphere). The analysis showed, in thefirst pass (between −80° C. and +250° C.), an exotherm (corresponding tothe opening of the oxazine rings, and to the crosslinking of thepolymer) above 200° C., with a maximum at approximately 230° C. Duringthe second and third DSC passes carried out between −80° C. and +250°C., no apparent glass transition (Tg) was visible.

5.3. Test of Adhesion in a Metal/Rubber Composite

A portion (650 mg) of the Polymer P-4 prepared above was dissolved in 8ml of DMA (N,N-dimethylacetamide; Sigma Aldrich product 38839), thisbeing in order to form a solution, a fraction (0.7 ml) of which wassubsequently deposited uniformly on a brass tape (film) havingdimensions of 10 cm×2.5 cm and a thickness of 0.4 mm; the assembly wasplaced in an oven at 175° C. (air ventilation) for 5 min and then for anadditional 5 min at 230° C. under vacuum in order, on the one hand, toremove any trace of solvent and, on the other hand, to at leastpartially (that is to say, completely or partially) open the oxazinerings of the polymer, this last stage being accompanied by a pronouncedchange in colour of the polymer, which changes to dark orange.

After cooling to ambient temperature, the tape provided at the surfacewith its thin (thickness 5 to 10 μm) layer of polybenzoxazine thusformed was subsequently subjected to a conventional two-stage adhesivecoating operation (two baths adhesive coating), first of all byimmersion in a first aqueous bath (approximately 94% water) based onepoxy resin (polyglycerol polyglycidyl ether, approximately 1%) and onisocyanate compound (caprolactam-blocked isocyanate compound,approximately 5%), which first adhesive coating stage is followed by adrying (2 min at 100° C.) and then a heat treatment (5 min at 200° C.).The tape thus treated was then immersed in a second aqueous bath of RFLadhesive (approximately 81% by weight of water) based on resorcinol(approximately 2%), on formaldehyde (approximately 1%) and on a rubberlatex (approximately 16% of NR, SBR and VP/SBR rubbers); finally, it wasdried in an oven at 130° C. for 2 min and then heat treated at 200° C.for 5 min.

The brass tape thus coated with the polybenzoxazine film and then coatedwith adhesive was subsequently placed between two layers of conventionalrubber composition for a belt reinforcement of a passenger vehicle tyre,which composition is based on natural rubber, on carbon black and silicaas filler and on a vulcanization system (sulfur and sulfenamideaccelerator); this composition was devoid of cobalt salt. Themetal/rubber composite test specimen thus prepared was then placed undera press and everything was cured (vulcanized) at 150° C. for 30 minunder a pressure of 20 bar.

After vulcanization of the rubber, excellent adhesive bonding betweenthe rubber matrix and the metal tape was obtained, despite the absenceof cobalt salt in the rubber matrix; this is because, during peel tests(at 20° C.), it was found that the failure occurred systematically inthe rubber matrix itself and not at the interphase between metal andrubber. Other adhesive bonding tests were carried out on a bright(uncoated) steel tape; they themselves also revealed an excellentadhesion to the rubber (systematic failure in the rubber matrix).

In conclusion, the benzoxazine according to the invention makes possiblethe synthesis of polymers giving the metal reinforcers the majoradvantage of being able subsequently to be adhesively bonded to rubbermatrices using simple textile adhesives, such as RFL adhesives, or elsedirectly (that is to say, without employing such adhesives) to theserubber matrices, for example when the latter contain appropriatefunctionalized unsaturated elastomers, such as epoxidized elastomers.Thus, use may be made of metal reinforcers coated or not coated withadhesive metal layers, such as brass, and also of surrounding rubbermatrices devoid of metal salts, in particular of cobalt salts.

Moreover, this constituting a significant advantage in comparison withthe other known polymers described in the introduction to the presentdocument, the polybenzoxazines resulting from the benzoxazines of theinvention have the remarkable ability, at high temperature, to opentheir oxazine rings and to thus result in a thermosetting polyphenolresin structure. This confers a better thermal stability on them.Finally, their specific microstructure makes it possible, veryadvantageously, to adjust the flexibility of the molecule according tothe particular applications targeted.

The invention claimed is:
 1. A halogenated benzoxazine compoundcorresponding to the formula: (A)

in which: Hal represents at least one halogen; each benzene nucleus ofthe two oxazine rings bears at least one halogen; and Z₁ and Z₂, whichare identical or different, represent an aliphatic, at least divalent,bonding group comprising at least one carbon atom and optionally atleast one heteroatom chosen from O, S, N and P.
 2. The halogenatedbenzoxazine compound according to claim 1, wherein Z₁ and Z₂, which areidentical or different, represent an aliphatic group comprising from 1to 12 carbon atoms.
 3. The halogenated benzoxazine compound according toclaim 2, wherein Z₁ and Z₂, which are identical or different, representa (poly)alkylene sequence comprising from 1 to 8 carbon atoms.
 4. Thehalogenated benzoxazine compound according to claim 3 corresponding tothe formula:

in which x₁ and x₂, which are identical or different, represent aninteger from 1 to
 8. 5. The halogenated benzoxazine compound accordingto claim 1, wherein Hal represents bromine, chlorine or fluorine.
 6. Thehalogenated benzoxazine compound according to claim 1, wherein eachbenzene nucleus of the two oxazine rings bears a single halogen.
 7. Thehalogenated benzoxazine compound according to claim 6, wherein thehalogen borne by each benzene nucleus of the two oxazine rings islocated in the para position with respect to the oxygen of the oxazinering.
 8. The halogenated benzoxazine compound according to claim 1,wherein Hal represents bromine.
 9. The halogenated benzoxazine compoundaccording to claim 4 corresponding to the formula:

in which x₁ and x₂, which are identical or different, represent aninteger from 1 to
 8. 10. The halogenated benzoxazine compound accordingto claim 9 corresponding to the formula:


11. A polybenzoxazine made by polycondensation of at least one compoundcorresponding to the formula:

in which: Hal represents at least one halogen; each benzene nucleus ofthe two oxazine rings bears at least one halogen; and Z₁ and Z₂, whichare identical or different, represent an aliphatic, at least divalent,bonding group comprising at least one carbon atom and optionally atleast one heteroatom chosen from O, S, N and P.
 12. The polybenzoxazineaccording to claim 11 made by polycondensation of a compoundcorresponding to formula (A), as a first monomer, with at least anaromatic diol or thiol compound, as a second monomer.
 13. Thepolybenzoxazine according to claim 12, wherein the aromatic diol orthiol compound corresponds to the formula (B):HX₁—Ar₁—Z₃—Ar₂—X₂H in which: X₁ and X₂, which are identical ordifferent, represent O or S; Ar₁ and Ar₂, which are identical ordifferent, represent a phenylene group; and Z₃ represents O or (S)_(n),n representing an integer equal to or greater than
 1. 14. Thepolybenzoxazine according to claim 13, wherein the aromatic diol orthiol compound corresponds to at least one of the formulae (B-1), (B-2)or (B-3):


15. The polybenzoxazine according to claim 11, wherein each benzenenucleus of the two oxazine rings bears a single halogen.
 16. A processfor the synthesis of a polybenzoxazine comprising the step of:polycondensating a compound corresponding to the formula:

in which: Hal represents at least one halogen; each benzene nucleus ofthe two oxazine rings bears at least one halogen; and Z₁ and Z₂, whichare identical or different, represent an aliphatic, at least divalent,bonding group comprising at least one carbon atom and optionally atleast one heteroatom chosen from O, S, N and P.
 17. The processaccording to claim 16, wherein the compound corresponding to formula(A), as a first monomer, is polycondensated with at least an aromaticdiol or thiol compound, as a second monomer.
 18. The process accordingto claim 17, wherein the aromatic diol or thiol compound corresponds tothe formula (B):HX₁—Ar₁—Z₃—Ar₂—X₂H in which: X₁ and X₂, which are identical ordifferent, represent O or S; Ar₁ and Ar₂, which are identical ordifferent, represent a phenylene group; and Z₃ represents O or (S)_(n),n representing an integer equal to or greater than
 1. 19. The processaccording to claim 18, wherein the aromatic diol or thiol compoundcorresponds to at least one of formulae (B-1), (B-2) or (B-3) below:


20. The process according to claim 16, wherein each benzene nucleus ofthe two oxazine rings bears a single halogen.